Dog Acting Weird And Crazy After Flea Medicine | What Should I Do?

Fleas and ticks can be a menace for dogs. They can cause intense itching. You will find your dog constantly scratching itself. It can cause severe levels of skin irritation. Moreover, fleas can also cause skin allergies and transmit other diseases.

This is a well-known problem in the canine world. Several flea treatments are available to prevent flea infestation among dogs. Topical, spot-on treatments are the most popular treatment administered.

Dog Acting Weird And Crazy After Flea Medicine-What Should Do
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Dog acting weird after flea medicine – is another problem that many pet parents have faced. Your dog showing symptoms like vomiting, trembling, disorientation, and seizure from a flea medicine is certainly not the reaction you would expect.

Your pet’s reaction can be confusing and overwhelming. The article will take you through signs, possible causes, and steps to follow when your dog acts crazy after flea medicine.

What Different Flea Treatments are Available?

What Different Flea Treatments are Available?
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The three broad categories of flea treatments recommended by pets are:

  • Dog flea collars
  • Topical flea treatments
  • Oral medications

Depending on the pet, their lifestyle, area they live in, you might need to follow a combination of treatments to fully protect your pet.

Dog flea collars are effective, but they tend to leave traces of chemicals in their surroundings. Young children and pregnant women should be kept away from these chemicals.

The same goes for the topical. These treatments are effective against fleas and other pests. When you apply the topical, the dog should be kept away from other pets and children. Some dogs can have allergic reactions to topical.

Oral medication is considered one of the safest flea treatments. The medicine is available in pill and chew form. Vomiting could be a side-effect of this treatment.

What are Flea Treatments Made Of?

What are Flea Treatments Made Of
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If your dog is ridden with fleas, using conventional flea treatments works best. The ingredients may differ from one brand to another, but most treatments contain ectoparasiticides – an antiparasitic drug.

Some standard ectoparasiticides used in flea treatments are:

#1. Pyrethrins

This is a pesticide that is naturally found in some chrysanthemum flowers. It attacks the nervous systems of insects. They are effective against fleas, mosquitoes, ticks, and flies.

#2. Pyrethroids

It is an organic compound similar to pyrethrins. Pyrethroids are available in various commercial products like pet sprays, shampoos, bug bombs, and other pest control products.

#3. Indoxacarb

It is an oxadiazine insecticide that effectively kills a wide variety of insects. It is a common ingredient for crop pesticides.

#4. Organophosphates

It is a compound derived from phosphoric or phosphoric acid. It is one of the widely used insecticides. It has applications in agriculture, garden, home, and veterinary practices.

#5. Fipronil

It is a broad-spectrum insecticide that affects the central nervous system of the insect. It is used to control ants, beetles, fleas, termites, cockroaches, and thrips among others.

Is Flea Medicine Toxic for Dogs?

Is Flea Medicine Toxic for Dogs
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Dog acting weird after flea medicine – well, the ingredient list and application process could be to blame.

As you have seen above, insecticide is a common ingredient used in flea collars and topicals. They surely are not the safest ingredients on the planet. These chemicals can have varying degrees of toxicity.

If you apply a larger dose than recommended or use a topical meant for a big dog on a smaller dog breed, the medicine can be toxic for dogs.

Your dog could accidentally ingest the medicine. For example, they lick the medicine-applied area or find an opened topical tube lying around. In such cases, your dog can act crazy or show signs of allergy or intoxication.

What Symptoms Indicate Adverse Reaction to Flea Medicine?

What Symptoms Indicate Adverse Reaction to Flea Medicine
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If your dog is behaving unexpectedly after the application of flea medicine, it could mean something has gone wrong with the application or the product itself.

In the case of an adverse reaction, it may show symptoms like:

  • Skin irritation
  • Skin redness
  • Vomiting
  • Diarrhea
  • Weakness
  • Excessive drooling
  • Excessive urination
  • Lack of coordination
  • Difficulty breathing
  • Tremors
  • Seizures
  • Depressed appearance

If the symptoms become severe, it is best to consult your vet immediately.

Why is the Dog Acting Weird and Crazy After Flea Medicine?

Flea treatments are common in dogs. The chemicals used are regulated by the EPA. And they are also well-tolerated by most dogs. But some dogs may not react well to the ingredients used in flea treatments.

Let us look at some of the possible causes why a dog starts acting weird and crazy after flea medicine.

#1. Natural Dislike

Natural Dislike
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Some dogs do not like the feeling of a liquid substance being applied to their body. So as soon as you apply the medicine, your dog could shake vigorously to get the liquid off its skin.

Some dogs are also sensitive when it comes to smell. The product might not smell any different to you, but that is not the case for dogs. For every human scent receptor, dogs have 50.

So, naturally, when they have a product on them that smells funny, dogs will behave restlessly, shake or run to get away from the smell.

Do not panic in such situations. Many pet parents have seen this reaction from dogs. It becomes a cause of concern when your pet shows additional symptoms like skin irritation or vomiting.

#2. Incorrect Treatment

The best and safest way to find the correct flea medicine for your dog is to ask your vet. Using over-the-counter medicine without considering the dog breed is not the way to go about it. Do not use medicines meant for humans or other animals on dogs.

Every medicine will come with its recommended dosage. If you use a higher dose, your dog’s skin could absorb those chemicals. Carefully read the directions available in the packaging.

If you use a flea medicine meant for larger dogs on a small dog, it could lead to serious complications. The intensity of the medicine can be toxic for the small dog.

#3. Allergies

It is difficult to predict what ingredient, food, or environmental factor can cause an allergy in dogs. The insecticide used in flea treatment could be the reason your dog is acting weird after flea medicine.

Once the skin absorbs the ingredients, they can trigger an allergic reaction. Your dog might start scratching excessively, their eyes start tearing, and they could cough and sneeze. Look at the area you have applied the medicine; it can become inflamed or develop skin lesions.

#4. Intoxication

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If your dog somehow ingests the flea medicine, it can be toxic for them. Flea medicine should ideally be applied to the area around the shoulder blades. For larger dogs, the medicine can be applied to the base of their tail. This is done, so your dog does not lick or rub the medicine off.

If the medicine is applied in easy to access areas, there are high chances your dog will lick it. Also, if you apply a large quantity of the topical, thinking more is better, the ingredient will be absorbed by the skin and enter the dog’s bloodstream.

There is a difference between treatments meant to kill external and internal parasites. Chemicals used in dog collars and topicals should not find their way inside your dog’s body.

What to do When Dog Acting Weird After Flea Medicine?

What to do When Dog Acting Weird After Flea Medicine
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Monitor your dog’s behavior once you have applied the medicine. Make a note of the date, time, name, and quantity of medicine used. Typically manufacturers recommend waiting 48 hours before bathing your pet after flea treatment. So, your dog’s reaction to the medicine can be immediate, or it can develop over time.

The reaction can occur even if the pet was fine with the product before. The manufacturer might have changed the ingredients or the composition of the product. Thus, you cannot be lax with your supervision.

If you see any of the adverse reaction symptoms mentioned above, you need to call your vet immediately. According to EPA, bathing your pet with mild soap and rinsing off with a large amount of water can help. Be careful not to use a chemical or perfume-laden soap, or it could accelerate the allergic reaction.

If the reaction is caused by a dog collar, get the collar away from the dog. In some cases, the symptoms subside once the irritant is removed from the dog’s body.

If your dog has ingested the medicine, you will have to take a trip to the vet’s clinic. Bring the medicine along as it can help the vet determine what could have triggered the reaction.

What Treatment Options are Available?

What Treatment Options are Available
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The treatment plan will depend on the product used, cause, and symptoms your dog is showing.

For example, in case of ingestion, the vet will give medicine to completely empty the bowel contents.

The vet could induce vomiting to rid the body of the allergen. But this depends on the product. In the case of some compounds, vomiting can do more harm than good. Thus, do not try to induce vomiting on your own; wait for the vet to decide.

Muscle relaxants can be given to manage tremors or seizures. If your dog becomes too weak or dehydrated, intravenous fluids will be administered.

What Mistakes to Avoid When Using Flea Medicine?

What Mistakes to Avoid When Using Flea Medicine
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When choosing a flea treatment for your dog, consider factors like dog breed, age, lifestyle, medical history, and the area you live in. With this information, your vet can determine the right type of medication.

Here are some mistakes to avoid when administering flea treatment:

  • Using ointments, creams or sprays meant for humans.
  • Not reading the instructions that come with the medicine packaging.
  • Buying a larger tube of topical meant for larger dogs, for your small dog, to save on money.
  • Applying medicine to areas your pet can easily lick.
  • Using medicine meant for dogs on puppies.
  • Combining different pest control treatments without vet consultation.

In addition, do not underestimate the behavior displayed by your dog. Some dogs can show their dislike for the product by shaking, restlessness, pacing, and lying on the ground. But in case of accompanying symptoms, do not waste time in reaching out to the vet.

What are the Safe Proactive Ways to Keep Fleas Away From the Dog?

What are the Safe Proactive Ways to Keep Fleas Away From the Dog
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If fleas have made themselves a home on your dog’s body, you will have to use flea treatments with insecticides. And as we have seen, these treatments are not always safe for dogs.

Instead, try to take proactive measures to keep fleas and other pests away from your pet.

1. Keep the Dog Clean

If your dog is prone to attracting pests, bathe them regularly. Use mild soap and water. Brush through the dog’s fur with a flea comb and drown the fleas in water. Regular brushing will keep their fur clean, healthy, and mat-free.

2. Keep the Dog’s Surroundings Clean

Thoroughly clean your dog’s bedding, toys, crate, or any other surface it frequently comes in contact with. Vacuuming, using hot soapy water can help keep pests away.

3. Keep Your Yard Well-Maintained 

If you have a green, flourishing yard, it is natural for it to attract pests like fleas. Mowing the lawn, removing thatch, using cedar mulch, avoiding over-watering are some ways to keep fleas away from your yard.

Sprinkling diatomaceous earth in your yard is a natural and effective way of killing fleas in your yard.

4. Keep Away From Natural Treatments

There are several flea treatments in the market that claim to be organic or natural. You should be wary of these products and not use them without vet consultation.

They may contain ingredients like lavender, eucalyptus, or tea tree oil. Lavender in higher quantities can be toxic to dogs. Eucalyptus, if ingested, can cause gastrointestinal and neurological issues.


Is your dog acting weird after flea medicine? The answer lies in the ingredient list of the product and application process.

Flea treatments like dog collars and topicals typically contain insecticides to effectively get rid of pests. Your dog could be allergic to insecticides in the product. Ingestion will trigger adverse reactions.

Watch for signs like skin irritation, vomiting, diarrhea, drooling, panting, or shivering. Consult with the vet immediately. They will suggest a treatment plan depending on the cause of the reaction.

Remember to choose an anti-flea treatment with the help of your vet. Follow the label instructions. Keep your dog and its surroundings clean.

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